A diffusion Monte Carlo method for charge density on a conducting surface at non-constant potentials

We develop a last-passage Monte Carlo algorithm on a conducting surface at non-constant potentials. In the previous researches, last-passage Monte Carlo algorithms on conducting surfaces with a constant potential have been developed for charge density at a specific point or on a finite region and a hybrid BIE-WOS algorithm for charge density on a conducting surface at non-constant potentials. In the hybrid BIE-WOS algorithm, they used a deterministic method for the contribution from the lower non-constant potential surface. In this paper, we modify the hybrid BIE-WOS algorithm to a last-passage Monte Carlo algorithm on a conducting surface at non-constant potentials, where we can avoid the singularities on the non-constant potential surface very naturally. We demonstrate the last-passage Monte Carlo algorithm for charge densities on a circular disk and the four rectangle plates with a simple voltage distribution, and update the corner singularities on the unit square plate and cube.

PEMETAAN POTENSI KERENTANAN PENCEMARAN AIR PERMUKAAN UNTUK PENGENDALIAN SANITASI LINGKUNGAN DI KABUPATEN BULELENG (Mapping on the potential vulnerability of surface water pollution for environmental sanitation control in Buleleng Regency)

One of the efforts to prevent water pollution is done by mapping of potential pollution vulnerability to support water quality control policy making. The research location is in Panas Sub-watershed, a part of the Saba Watershed which originates on the northwest slope of the Bratan Volcano Complex and upstream is Lake Tamblingan, Buleleng Regency. The objectives of the study include: 1) mapping the parameters of potential surface water pollution vulnerability, 2) mapping land cover changes in 2000 and 2016, 3) mapping the potential surface water pollution vulnerability and its dynamics in 2000 and 2016, and 4) formulating a management recommendation to control surface water pollution. Mapping the potential surface water pollution vulnerability was conducted by GIS and Point Count System Model (PCSM) method using parameters of slope, land cover, and annual average rainfall. The results showed that some of the upstream and middle areas of the Panas Sub-watershed were categorized as high potential vulnerability caused by steep slopes, plantation cover, and annual average rainfall of 2,251 - 2,500 mm/year. Various recommendations to control surface water pollution are conducting integrated waste management individually or in groups, such as collectively septic tank construction, waste disposal organization, and waste water management installation; providing directions for appropriate land cultivation for farmers so that the pollutant load due to the use of pesticides could be controlled; as well as controlling and supervising the tourist area around Tamblingan Lake.

Structural properties and adsorption of uranyl ions on the nanocomposite hydroxyapatite/white clay

Uranium is more and more extensively applied as a source of energy and can be potentially used for nuclear weapon production. Owing to that fact, the problem of uranium expansion in the environment is the object of research and draw attention many scientists. One of the most effective methods of uranium removal from the wastewater (where uranium is present in a low concentration and occurs mainly in the form of uranyl ion, UO22+) is the adsorbent usage. It is important to discover an adsorbent which will be effective, widely available and cheap. The paper discusses properties and the ability of U (VI) adsorption on a clay and nanocomposite clay/Hap (hydroxyapatite) obtained by wet method. The adsorbents were characterized by the mentioned below tests: XRD, XRF, the porosity (nitrogen adsorption–desorption method), zeta potential, surface charge density and sorption of U (VI). It was shown that nanocrystalline composites Hap/white clay can be appropriate adsorbent for removal of uranyl ions. The adsorption depends on the temperature and pH of the solution.

Stocks drift and vortex instability of the potential surface wave

<p>It is shown that in the case of potential surface wave an exact solution of the equations of the nonlinear Lagragian’s dynamics of the fluid particle has the drift velocity as an eigenvalue. The fluid particle trajectory is a circular rotation around a center point moving with a constant drift velocity. The rotation frequency differs from the wave frequency by the Doppler’s shift caused by the drift velocity. The constant drift velocity, for the surface wave of small amplitude, coincides with the classical expression for the Stokes drift velocity.</p><p>It is also shown that in the cases with absence of the Stokes drift and with presence of the Stokes drift the vortex instability of a potential surface wave has the same futures. But the vortex temporal variability in the case of the Stokes drift is affected by the Doppler’s shift caused by the Stokes drift velocity. Hence it allows a conclusion that the vortex instability of a potential surface wave initiates turbulent mixing and Lengmure circulation in the ocean upper layer.      </p><p> </p>

The effect of composite PHB coating on the biological properties of a magnesium based alloy

Magnesium alloys have been widely investigated as biodegradable cardiovascular temporal implants due to their better mechanical properties and biocompatibility, but the rapid degradation limited its application. In this study, the anodic oxidation-Cu structure was used to improve the adhesive strength and stability between poly-β-hydroxybutyrate (PHB) and magnesium alloys, and the effects of anodic oxidation magnesium alloys with copper film and PHB film (MACP) on human umbilical vein endothelial cells (HUVECs), blood compatibility and antibacterial properties were investigated in this research. As the result, the MACP structure had a stable structure and better corrosion resistance, and significant antibacterial properties. The coating would not affect the original excellent biocompatibility of the magnesium alloy. It was indicated that MACP was a potential surface modification strategy for vascular stents candidate material.